The invention relates to a rotor for a synchronous machine, in particular a reluctance machine, said rotor comprising a cylindrically constructed, magnetically soft element, wherein the magnetically soft element comprises cut-outs for the purpose of forming magnetic flux barriers that form an even number of salient magnetic poles.
Rotors for synchronous reluctance machines are typically equipped with a cylindrical, magnetically soft element that is arranged in a coaxial manner on the rotor axis. The magnetically soft element comprises flux conducting sections and also flux barrier sections for the purpose of forming at least one pole pair or rather gap pair and said flux conducting sections and flux barrier sections differ from one another to a varying degree of salient pole magnetic permeability. The section having a high magnetic conductivity, as is generally known, is characterized as the d-axis of the rotor, and the section having a comparably lower conductivity is characterized as the q-axis of the rotor. An optimal torque yield then occurs if the d-axis comprises an as high as possible magnetic conductivity and the q-axis comprises an as low as possible magnetic conductivity.
This object is often achieved by means of forming several cut-outs in the magnetically soft element along the q-axis and said cut-outs are filled with air, whereby the magnetic flux is inhibited in the direction of the q-axis and, as a consequence, the permeability decreases. The magnetically soft element that is constructed in this manner is subsequently attached to a rotor shaft and is fixed in an axial and also tangential manner.
The object of the present invention is to further develop a salient rotor of this type for a synchronous machine, in particular for a reluctance machine, in order to optimize the ratio of the salient pole magnetic permeabilities that differ from one another to a varying degree along the d-axis and the q-axis. Furthermore, the object of the invention is to further develop the construction of a rotor of this type in order in particular to simplify its production process.
For the purpose of achieving the object, it is provided that at least one cut-out within the cylindrically constructed magnetically soft element is filled at least in part with a diamagnetic or paramagnetic medium in lieu of air. In particular, as a result of selecting a diamagnetic medium in lieu of air, it is possible to increase the difference of the permeability between the q-axis and d-axis.
It is preferred that the cut-outs are entirely filled with the diamagnetic medium. In particular, it is possible for all cut-outs of the magnetically soft element to be entirely filled with the diamagnetic or paramagnetic medium. In this case, it is particularly advantageous if the entire diamagnetic or paramagnetic medium represents only a single component.
Furthermore, it is also possible to use the diamagnetic or paramagnetic medium in accordance with the invention as a constructive element for the purpose of constructing the rotor. In this case, the diamagnetic or paramagnetic medium represents a carrier medium for the purpose of receiving the magnetically soft element, wherein the function of the medium as a carrier is advantageous in particular in the case of a single component embodiment of the diamagnetic or paramagnetic medium. It is preferred that the magnetically soft element can be fixed in a very simple manner to the rotor shaft in the axial direction with the aid of the diamagnetic or paramagnetic carrier medium.
Metal end discs that are known from the prior art for the purpose of fixing a magnetically soft element of this type to the rotor axis are superfluous and can be entirely replaced by means of the diamagnetic or paramagnetic medium being used. In particular, end discs that are embodied from the diamagnetic or paramagnetic medium can be formed on the end surfaces of the cylindrical, magnetically soft element and said end discs are used for the purpose of fixing the magnetically soft element to the rotor shaft in the axial direction.
The preferred embodiment of the rotor in accordance with the invention renders it possible for the magnetic barrier effect to be achieved and also for the process of axially fixing the magnetically soft element to be performed by means of a single component, i.e. the diamagnetic or paramagnetic carrier medium. As a consequence, the diamagnetic or paramagnetic carrier medium together with the magnetically soft element forms the two single components of the composite rotor in accordance with the invention.
In a preferred embodiment of the rotor in accordance with the invention, the magnetically soft element is a lamination stack that—as is known from the prior art—is constructed from several metal sheets that are stacked one on top of the other in the axial direction of the rotor. This construction prevents the occurrence of eddy currents in the magnetically soft element. An alternative method is available, whereby the magnetically soft element being used is produced in accordance with a powder-metallurgical method.
The lamination stack comprises individual metal lamina, wherein each individual metal lamina comprises along the q-axis several flux barriers that are filled with a diamagnetic or paramagnetic medium. In particular, one construction of the lamination stack is disclosed in U.S. Pat. No. 5,818,140 which is explicitly referred to in this context. In accordance with the teachings of the present invention, the corresponding cut-outs, in other words the flux barriers that are formed, are then filled with a diamagnetic or a paramagnetic medium in lieu of air.
It is preferred that at least two adjacent metal sheets of the lamination stack can be arranged spaced apart with respect to one another in the axial direction. In this case, it is possible for the intermediate space that is formed between the adjacent metal laminae to be filled at least in part by means of the diamagnetic or paramagnetic medium. This preferred construction of the rotor increases the stability of the rotor during operation. The radial forces that occur on the motor are absorbed by means of the diamagnetic or paramagnetic carrier medium. It is not necessary to provide radial supporting ribs that are frequently used within the individual metal sheets and that were hitherto necessary in specific embodiments for the purpose of radially reinforcing the lamination stack.
It is preferred that the diamagnetic or paramagnetic carrier medium fills the entire cylindrical intermediate space between individual metal sheets in a continuous manner.
It is possible that in each case two metal sheets are arranged spaced apart with respect to one another in regular spacings in the axial direction of the lamination stack in order to provide additional space for the diamagnetic or paramagnetic medium.
It is likewise feasible that the spaced arrangement of the two adjacent metal sheets is achieved by means of inserting a distance element. It is preferred that annular distance elements are used, wherein the intermediate space that lies in the radial direction above the distance elements is filled by means of the diamagnetic or paramagnetic carrier medium.
A modified metal lamina of the magnetically soft element is also feasible, wherein a tangential section of the magnetically soft element that is missing in the region of the q-axis on the outer circumference is completed by means of the diamagnetic or paramagnetic medium. As a consequence, the portion of space of the magnetically soft element that is missing from the full cylinder is likewise formed by means of the diamagnetic or paramagnetic carrier material.
Magnetically soft element parts lie between, in each case, two adjacent cut-outs along the q-axis of the magnetically soft element and said magnetically soft element parts are generally connected to one another in a magnetically conductive manner. In a particularly preferred embodiment of the invention, the conductive magnetically soft element parts that are formed between, in each case, two flux barriers are connected one to the other in a magnetically non-conductive manner. As a consequence, the difference of the permeability along the d-axis and the q-axis is further increased. In this case, the process of radially and axially fixing the magnetic elements is entirely performed by means of the diamagnetic or paramagnetic carrier material.
The diamagnetic or paramagnetic medium being used preferably comprises polymers and/or duromers and/or ceramic and/or glass and/or wood.
The invention further relates to a method for producing a rotor according to an above described embodiment. In accordance with the invention, the magnetically soft, cylindrical element is constructed in a first method step, and in a second method step, the diamagnetic or paramagnetic medium is introduced into or rather attached around the constructed magnetically soft element by means of a primary forming production method.
By way of example, in the case of the embodiment of the magnetically soft element as a lamination stack, in a first method step, a multiplicity of identical metal sheets are stacked one on top of the other in the axial direction. In the second method step, the diamagnetic or paramagnetic medium is introduced into the cut-outs of the individual metal sheets by means of the primary forming production method, in particular injection molding, wherein, where necessary, end discs are likewise formed from the diamagnetic or paramagnetic medium for the purpose of fixing the lamination stack to the rotor axis. It is expedient if the necessary diamagnetic or paramagnetic medium is entirely embedded in a cast in the lamination stack and as a consequence, only represents a single component. The diamagnetic or paramagnetic medium that extends through the lamination stack achieves both the magnetic barrier effect and also performs the process of axially fixing the lamination stack. In cooperation with the lamination stack, the resulting composite rotor is constructed from only two individual components.
In a similar manner to this, the rotor in accordance with the invention is produced on the basis of a material that is produced in accordance with a powder-metallurgical method. Initially, the desired form of the magnetically soft, cylindrical element is formed by means of the material, wherein likewise corresponding cut-outs are provided. The cut-outs are filled in a second method step with the diamagnetic or paramagnetic medium.
Furthermore, the present invention relates to the use of the rotor in accordance with the invention, in particular according to one of the above mentioned advantageous embodiments, in a reluctance machine, in particular in a synchronous reluctance machine.
Furthermore, the invention is intended for use in a reluctance motor, in particular a synchronous reluctance motor, said reluctance motor being equipped with the rotor in accordance with the invention, in particular the rotor in accordance with one of the above mentioned advantageous embodiments. The reluctance motor evidently comprises the same characteristics and advantages as the rotor in accordance with the invention in accordance with any of the advantageous embodiments and for that reason a description is not repeated at this point.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.